Edward, I've grown tulsi or holy basil (Ocimum tenuiflorum) in my garden in the Bay Area. If you can grow Italian basil, you can grow holy basil. Have you searched online for it under its Latin name "Ocimum tenuiflorum" or "Ocimum sanctum"? Specialty nurseries may sell the plants. You can buy seeds online. The website Dave's Garden lists vendors.
http://davesgarden.com/guides/pf/go/930/
Horton Spice Mills is selling culinary Italian basil. Holy basil is a specialty plant and not that readily available.
As far as I know, holy basil is usually associated with Southeast Asian cooking, not Japanese cooking. It has a spicy flavor. The plant is considered medicinal in the Indian Ayurvedic tradition, but I wouldn't call it a drug in the conventional sense. It is an herb that is supposed to promote health and well-being. It's also popular in Thai stirfries, which is how I use it.
